1. Field of the Invention
The present invention relates to devices and methods for attenuating sound and more specifically relates to a sound attenuating trailer assembly for a portable machine, such as a portable air compressor.
2. Description of the Prior Art
Noise generated by motors, engines and/or machinery is typically transmitted to the environment via structural or airborne paths. The specific level of noise transmitted by these airborne paths may be reduced by surrounding the motor, engine or machine with an enclosure. These sound reduction efforts are often made in response to federal, state and local regulations that may require machine operators to take affirmative steps to minimize the level of noise generated during operation of a machine.
There have been a number of attempts directed toward reducing the level of noise generated by a motor, engine and/or machine.
U.S. Pat. No. 3,642,092 to Cederbaum discloses a power plant with a power unit enclosed by a casing forming a sound-absorbing chamber with walls having an outlet for consumed air and an inlet for cooling air and combustion air as well as a number of labyrinth-like sound reducing passages. The labyrinth passages are arranged so that cooling air is caused to travel along the power unit and is passed through a labyrinth passage in the wall opposite the inlet, thus forming an outlet for heated air.
U.S. Pat. No. 4,347,043 to Morris discloses a compressor unit for compressing a vapor, a motor for driving the compressor, a shell encompassing the compressor and motor, and a supply of lubricant disposed within the shell. The compressor unit further includes a perforated lining positioned adjacent to the shell and annularly extending around the compressor for capturing a thin film of lubricant between the shell and the lining for damping noise generated by the motor.
U.S. Pat. No. 4,982,812 to Hwang discloses a noise-preventive apparatus for a compressor including a double-wall vacuum jacket encompassing a compressor therein so that the noise generated during operation of the compressor will not be transmitted outwardly through a vacuum chamber, thereby preventing noise pollution.
U.S. Pat. No. 5,804,775 to Pinnington discloses an acoustic enclosure for the reduction of noise transmission from monopole, quadrapole and higher order noise sources. The enclosure has an approximately spherical shaped outer wall, which is made from stiff materials to reduce the amount of stretching of the enclosure wall. The enclosure substantially encases the noise source.
Although the above-identified patents disclose enclosures for damping the level of noise transmitted by motor, engine or machine, there remains a need for an enclosure for a portable machine capable of effectively attenuating noise. In particular there is a need for a sound attenuating enclosure for a portable compressor.
Portable air compressor systems generally include an air compressor mounted upon a trailer and having a protective enclosure or cover secured over the top of the compressor, such as the portable compressor disclosed in commonly assigned U.S. Pat. No. 5,518,262, the disclosure of which is hereby incorporated by reference herein.